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From "Andrus Adamchik (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CAY-2123) Synchronizing cache updates with external transaction boundaries
Date Mon, 17 Oct 2016 11:57:58 GMT

     [ https://issues.apache.org/jira/browse/CAY-2123?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Andrus Adamchik updated CAY-2123:
---------------------------------
    Summary: Synchronizing cache updates with external transaction boundaries  (was: Synchronizing
cache updates with external trasnaction boundaries)

> Synchronizing cache updates with external transaction boundaries
> ----------------------------------------------------------------
>
>                 Key: CAY-2123
>                 URL: https://issues.apache.org/jira/browse/CAY-2123
>             Project: Cayenne
>          Issue Type: Bug
>    Affects Versions: 3.1.1, 4.0.M3
>            Reporter: Andrus Adamchik
>            Assignee: Andrus Adamchik
>
> Some of the steps in the commit sequence should work differently when Cayenne is operating
under external transactions. One scenario is shared cache synchronization. E.g.:
> 1. Thread A commits ObjectContext. Under external transaction this results in a flush
operation, pending tx commit/rollback
> 2. Thread B runs an operation that hits the cache (e.g. reads a to-one relationship).
It gets values committed under thread A, but not yet visible in the DB (an example of a dirty
read ... incorrect behavior already).
> 3. Thread A rolls back its transaction... Invalid value gets stuck in shared cache for
all other threads to see.
> This behavior results in dirty reads regardless of the actual transaction isolation level.
Looks like we'll need to make our cache transaction-aware and provide an API for committing
cache state on external transaction events. The initial implementation for this API may be
targeting Spring transactions.
> Things may become even more complicated when multiple overlapping threads change the
same object. "snapshot version changed" message in the logs is a symptom of this inconsistency.




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